Pakistani security forces have arrested three men said to be agents of Indian intelligence agency Research and Analysis Wing (RAW), a media report said on Tuesday.
The arrested men, who were described as Afghan nationals, were held from the northwestern tribal areas.
"During investigations they have admitted that were plotting to (provoke) sectarian and linguistic clashes in different areas of the country, including Sindh," Online news agency reported.
"Evidence with regard to the involvement of RAW in the recent blasts in Karachi has also been dispatched to Sindh government," the agency added, quoting security sources.
Twenty-seven people died and more than 100 were wounded in the twin bomb blasts February 5. In December, a suicide bomber blew himself up during a Muharram procession in the city, killing 40 people and wounded dozens more.